1. Field of the Invention
The present invention relates to an electronic circuit and a semiconductor device and, more particularly, to an electronic circuit and a semiconductor device that operate by using a plurality of types of power supply voltages.
Various kinds of digital circuits such as a memory or a microprocessor are integrated on a semiconductor device. Further, the semiconductor device is provided with a power-on reset circuit so as to prevent malfunction from occurring in such digital circuits when a power supply voltage is supplied thereto.
The power-on reset circuit detects whether or not the power supply voltage supplied to a digital circuit (internal circuit) integrated on the semiconductor device exceeds or not a predetermined voltage value (specified voltage value) suitable for operating the digital circuit. When the power supply voltage exceeds the specified voltage, the power-on reset circuit resets, e.g., a flip-flop circuit constituting the digital circuit to an initial state to prevent the flip-flop circuit from being in an indefinite state. Thereafter, the power-on reset circuit cancels the reset, and the digital circuit resumes its operation. With this configuration, the digital circuit can be prevented from malfunctioning when the power supply voltage rises.
A digital circuit that operates using a plurality of types of power supply voltages, i.e., a plurality of different power supply voltages is provided with a plurality of level conversion circuits for signal propagation therein. In this case, malfunction may occur when any one of the plurality of power supply voltages is lowered. In such a case, the power-on reset circuit cannot sufficiently prevent malfunction of the digital circuit.
For example, JP- 2005-102086-A describes, as the digital circuit, a level shift circuit.